Theiler's murine encephalomyelitis virus (TMEV) induces chronic inflammatory demyelinating disease in susceptible mice. Moreover, the initial demyelination induced by TMEV infection leads to the development of Th response to myelin autoantigens. In light of the potential viral etiology and similarities in the progression of chronic demyelination, the TMEV system is considered to be a relevant animal model for studying human multiple sclerosis (MS). Previously, we have identified the major epitopes of viral capsid proteins recognized by Th cells in the periphery of TMEV-infected susceptible SJL mice. By utilizing an overlapping peptide library representing entire capsid proteins, we have now identified epitopes recognized by CNS-infiltrating CD4 + and CD8 + T cells in resistant C57BL/6 as well as susceptible SJL mice. In addition, we have recently demonstrated that spontaneously arising variant viruses that do not cause demyelination preferentially induce a Th2 response in mice and Th2-promoting cytokines in antigen presenting cells. Furthermore, we have generated transgenic lines immunologically tolerant to capsid epitopes and expressing TCR specific for a major VP2-epitope. Interestingly, our preliminary results utilizing primary glial cell cultures (astrocytes, oligodendrocytes and microglia) strongly suggest that production of several proinflammatory chemokines and cytokines with delayed production of Type I IFN are induced upon TMEV infection. Based on these observations, we hypothesize that initial cellular gene activation by viral infection plays a critical role in the initiation and progression of virus-induced, immune-mediated demyelination by facilitating early recruitment of inflammatory immune cells to the CNS as well as by sustaining the inflammatory response. To test these possibilities, we propose the following specific aims. 1. Compare the level, specificity and type of CNS-infiltrating Th cells in resistant and susceptible mice during the course of TMEV-infection. 2. Analyze cytokines/chemokines directly induced in vitro by TMEV infection in glial and antigen presenting cells and elucidate their role in viral replication/persistence. In addition, the molecular mechanisms of gene activation by TMEV will be determined. 3. Investigate the role of innate immunity in cellular infiltration, viral persistence, induction of TMEV-specific immunity and consequent development of demyelinating disease. We believe that our proposed studies will yield important information on the potential roles of virus-specific T cells and CNS glial cells in the initiation and maintenance of inflammatory responses leading to eventual demyelinating disease. [unreadable] [unreadable]